The invention relates to calibrating a real time clock (RTC) and more particularly to a method for calibrating an RTC that utilizes an average method of calibration.
Real Time Clocks (RTC) are essential components of many electrical devices. RTCs utilize crystals for performing timing functions. The crystals oscillate at a predetermined frequency, and a counter is updated by one second after a predetermined number of oscillations. The frequency of oscillations varies with temperature, however, so the precision of the crystals will be affected when environmental conditions change. The quality of the crystals also affects the precision. This means that, in certain situations, the crystals will oscillate faster or slower than expected so the predetermined number of oscillations will not exactly equal one second and the clock timing becomes inaccurate. In these situations, calibration needs to be performed to correct for the timing errors.
If the accumulated offset is relatively large then a significant ‘jump’ will occur at the point of calibration. This can be distracting to a user.